The present disclosure relates to a full-jacket helical conveyor centrifuge including a rotatably disposed, metallic drum with a horizontal axis of rotation. Also included is at least one drive device for the drum. A helical conveyor is also included which is rotatably disposed at a differential rotational speed with respect to the rotational speed of the drum. The helical conveyor can be rotated by a gearing by the at least one drive device for the drum or by another device.
It is known to drive centrifuges in many different manners. In the field of full-jacket helical conveyor centrifuges, it has caught on to equip the helical conveyor and the drum respectively with a driving device in order to be able to control these two elements separately from one another without any tie to a fixed transmission ratio. Such a state of the art is known from German Patent Document DE-A-2811887 or DE 1732887.
For driving the drum, a belt drive is generally used which has been successful in practice but which requires a relatively large amount of space and therefore, because of frictional heat in the event of a belt slip, generates high temperature at the belts and the pulleys and is also often relatively loud. A demand therefore exists for alternative drive concepts where a belt drive is avoided.
For example, in the case of laboratory centrifuges, electromagnetic drives are also known; such as magnets in a rotating beaker glass. Furthermore, from European Patent Document EP 0 930 099 B1, an electromagnetic transmission for driving a laboratory centrifuge is known which is connected behind an electric motor but which is not suitable for larger centrifuges, such as full-jacket helical conveyer centrifuges. A spinning centrifuge in the manner of a magnetic drive is also illustrated in German Patent Document DE 74 26 623 U1.
The use of an axial-field electric motor in the case of a sugar drum-type centrifuge without a helical conveyor is also known from German Patent Document DE 33 25 566 C2. In contrast, a use on a full-jacket helical conveyor centrifuge has so far not been considered, probably because this type of centrifuge always also requires a drive for the helical conveyor and because an excessive heating of the product by way of the drum was also feared. An analogous situation applies to the solutions of German Patent Document DE 40 08 945 C2, which shows an evaporator—concentrator centrifuge, and German Patent Document DE 38 34 222 C2.
The present disclosure relates to a full-jacket helical conveyor centrifuge having a drive as an alternative to a belt drive.
The present disclosure further relates to a full-jacket helical conveyor centrifuge including a rotatably disposed drum and a drive device for the drum. The drive device for the drum includes at least one electromechanical direct drive having secondary elements arranged on the outer periphery of the drum or on the outer periphery of a part non-rotatably connected with the drum. Primary elements are arranged radially outside the secondary elements at a distance from the secondary elements and without contact. A propulsion force is generated by an electromagnetic field of travelling waves.
Accordingly, the drive device for the horizontally disposed drum has at least one electromechanical direct drive, whose primary or secondary elements are arranged directly at or on the drum or whose primary and secondary elements are arranged at or on a part non-rotatably connected with the drum, and whose corresponding secondary or primary elements are arranged at a distance outside the drum or the part non-rotatably connected with the latter with no contact between these. A propulsion force is generated without gears by an electromagnetic field of travelling waves which advances outside the drum around the metallic drum or around the part non-rotatably connected with the latter. This can be implemented, for example, by a large number of successively controllable coils on the outer periphery of the drum which are used as the primary elements for generating the field of travelling waves in order to, in the process, take along a large number of the permanent-magnetic secondary elements.
Thus, a simple concept of a field of travelling waves, which is generated directly without an electric motor on the input side and which advances, for example, on the outer periphery of the drum around the drum and does not penetrate the latter like a rotating field, is utilized also for the direct drive of a centrifugal drum of a decanter with a helical conveyor. According to the present disclosure, the helical conveyor can also be driven in manner different from that of the drum, for example, by a conventional rotating-field electric motor. The problem of the heat development of a product by the drum can also, against all expectations, be controlled in the case of a full-jacket helical conveyor centrifuge. In addition, a continuous rotational speed adjustment can take place without a frequency converter.
A ratio between the inner axial dimension of the drum and its inside diameter is greater than 1, and may be greater than 2.5. For such drums, the “field of travelling waves drive” can be accommodated in an area of the elongated drum without interfering with function elements at the axial ends of the drum.
According to the present disclosure, a belt drive for the drum can be eliminated. Instead, an electromagnetic gearless direct drive is used for the drum, which direct drive has a compact construction while the torque is high and is easily controllable in a low-noise manner. As a result, a safety advantage is also obtained because the drum can be braked particularly rapidly by the direct drive.
The secondary elements of the at least one direct drive are arranged on the outer periphery of the drum or on the outer periphery of a part non-rotatably connected with the drum. The primary elements are arranged radially outside the secondary elements at a distance from these with no mutual contact. By this arrangement, a compact embodiment is implemented and permits the complete elimination of a gear. Disadvantageous axial forces upon the bearing are avoided.
The present disclosure is applicable for a use in the case of full-jacket helical conveyor centrifuges. There are many points of the drum of this type of a centrifuge on which, depending on the performance and constructively geometrical situation, one or more electromagnetic direct-drive devices for the drum can be arranged. The compact arrangement is advantageous here because the drive device can be integrated completely into the decanter frame or the machine frame. Further advantages are the low generating of noise and, under certain circumstances, even vibration-damping characteristics. The forces acting upon the drum bearing which would be applied by a belt drive are eliminated.
It is possible that several of the electromagnetic direct drives may also be arranged on the drum or the part non-rotatably connected with the drum.
The drum itself, particularly its cylindrical section from a constructive point of view, may offer a preferred site of the arrangement of the direct drive. Although a thermal influence affects the drum and the centrifugal material in this area, it generally can be kept low.
If, on the other hand, an attachment is used as an axial extension of the drum for arranging the direct drive, an additional heat development of the product area by the drum is avoided. Nevertheless, a drive directly on the drum between the two main bearings may be preferred, because here also negative loads of the drive upon the main bearings can be largely avoided.
The primary or secondary elements surround the drum completely or in sections concentrically. The arrangement in sections thereby may simplify the constructive expenditures.
It is also conceivable that the primary or secondary elements are arranged on a ring disk projecting radially from the drum or a part non-rotatably connected with this drum. The ring disk is non-rotatably connected with this drum or part, and the corresponding secondary or primary elements are arranged on a non-rotatable ring disk or on a ring, which is arranged, for example, in an axially offset manner parallel to the co-rotating disk.
The present disclosure is applicable to the full-jacket helical conveyor centrifuge such as, the so-called decanter having a helical conveyor, where a belt drive for the drum can be replaced. The helical conveyor can be driven in a different manner; for example, hydraulically or mechanically or by a gearing between the drum and the helical conveyor or by another direct drive with a field of travelling waves arrangement. In this case, a gearing between the drum and the helical conveyor can also be eliminated.
The present disclosure addresses a full-jacket helical conveyor centrifuge with a rotatably disposed metallic drum and a rotatable helical conveyor as well as a drive device for the drum and a drive device for the helical conveyor. At least the drive device for the helical conveyor has at least one electromechanical direct drive whose primary or secondary elements are arranged directly at or on a part non-rotatably connected with the helical conveyor, and whose corresponding secondary or primary elements are arranged without contact at a distance outside this part. A propulsion force being generated without gears by an electromagnetic field of travelling waves advances around the part non-rotatably connected with the helical conveyor. In this manner, a gearing between the drum and the helical conveyor could even be eliminated, so that the two elements can be controlled completely independently of one another. In this case, it may be advantageous to further develop both drives, that is, the drive for the drum and that for the helical conveyor, as a direct drive.
It is conceivable that the drum and/or the helical conveyor have at least one play-free bearing around which or directly adjacent to which the respective electromagnetic direct drive is arranged.
The drive device for the helical conveyor may be constructed independently of the drive device for the drum.
It is conceivable that another co-rotating field of travelling waves motor is included to generate the required differential rotational speed between the helical conveyor and the drum. Should this motor be only to generate the differential rotational speed, it may have small dimensions and therefore be cost-effective.
Other aspects of the present disclosure will become apparent from the following descriptions when considered in conjunction with the accompanying drawings.